1. Field of the Invention
The present invention relates to an ultrasound probe and an ultrasound diagnostic imaging apparatus.
2. Description of Related Art
Since ultrasound allows to examine inside of a subject in a non-destructive and harmless way, it has been applied in various fields such as inner defect examination, disease diagnosis and the like. As one example, ultrasound is applied to an ultrasound diagnostic imaging apparatus which visualizes the inner condition of a subject on the basis of a received signal generated from reflection ultrasound from inside of the subject by scanning inside the subject with ultrasound.
Such ultrasound diagnostic imaging apparatus is provided with an ultrasound probe which transmits and receives ultrasound to and from a subject. The ultrasound probe is provided with a plurality of piezoelectric devices each of which generates ultrasound by vibrating mechanically based on a driving signal and generates a received signal by receiving reflection ultrasound caused by the acoustic impedance difference in the subject by utilizing the piezoelectric phenomena.
The ultrasound probe is provided with an acoustic lens which focuses the ultrasound output from the piezoelectric devices in a slice direction and an acoustic matching layer which is arranged between the piezoelectric devices and the acoustic lens and which matches the acoustic impedance of the piezoelectric devices and the subject. Further, the ultrasound probe is provided with a backing layer for reflecting, attenuating and absorbing the ultrasound which is emitted backward from the ultrasound probe, the backing layer being provided on the back side of the piezoelectric devices. Here, it is known that by providing three or more acoustic matching layers, sensitivity and responsiveness of the ultrasound probe can be improved (for example, see JP Shou60-185499).
With respect to such ultrasound probe, there is known a technique which increases the ultrasound energy to be output frontward by providing an acoustic reflecting layer between the piezoelectric devices and the backing layer and reflecting the ultrasound output from the back of the piezoelectric devices toward front (for example, see U.S. Pat. No. 6,685,647). In order to improve its sensitivity and resolution in terms of distance direction, it is expected that the ultrasound probe has characteristics such as broadband, low loss and low ripple.
However, if an acoustic reflecting layer is further provided in the ultrasound probe whose overall layer thickness has increased by being provided with a plurality of acoustic matching layers, there may be a case where ripples are generated due to ultrasound reflecting in the ultrasound probe and unwanted resonance being included in the transmission and reception band of the ultrasound output from the ultrasound probe. In such case, there is a problem that the quality of the ultrasound image to be generated drops.